Tape feeding means



June 14, 1960 T. c. GAMS ETAL 2,941,124

TAPE FEEDING MEANS Original Filed April 26, 1952 5 Sheets-Sheet 1 FIG!m5 m MG V C m E R 0 w w T PAUL J.K!EFER JR.

ATTORNEY June 14, 1960 "r. c. GAMS ETAL 2,941,124

TAPE FEEDING MEANS Original Filed April 26, 1952 5 Sheets-Sheet 2 U:INVENTORS. THEODOREQGAMS I PAUL J. KIEFER JR. L' BY him/60 /0 ATTORNEYJune 14, 1960 T. c. GAMS ETAL TAPE FEEDING MEANS Original Filed A ril26, 1952 5 Sheets-Sheet 3 INVENTORS DORE 6.6AMS

J. KIEFER JR.

ATTORNEY "r. c. GAMS ETAL 2,941,124

TAPE FEEDING MEANS 5 Sheets-Sheet 4 w QI June 14, 1960 ori inal FiledApril 26, 1952 BY W W ATTORNEY June 14, 1960 T. c. GAMS ETAL TAPEFEEDING MEANS Original Filed April 26, 1952 5 Sheets-Sheet 5 l Qwmiukki1N VEN TORS THEODORE C. GA M5 wwm PAUL J.K|EFER JR. BY Mai ZIQLMWATTORNEY United States Patent TAPE FEEDING MEANS Theodore C. Gams,Monsey, N.Y., and Paul J. Kiefer, Jr., Clifton, N.J., assignors, bymesne assignments, to Curtiss-Wright Corporation, Carlstadt, N.J., acorporation of Delaware Original application Apr. 26, 1952, Ser. No.284,597, now Patent No. 2,778,634, dated Jan. 22, 1957. Divided and thisapplication Apr. 17, 1956, Ser. No. 582,902

3 Claims. (Cl. 317-123) This invention relates to means for feedingstrip mate rial, particularly magnetic record strip material or tape, atvery high speed past operating means.

This application is a division of application Serial No.- 284,597, filedApril 26, 1952 and is now Patent 2,778,634.

The tape is of thin, relatively fragile and flexible material. It isintended to bear closely spaced lines of magnetically recordeddesignations, with a number of successive lines being grouped toconstitute a data block. The line spacing may be as close as .01 inchand the interblock spacing as small as .4 inch. It is desired to feedthe tape at very high speed as, for instance, at a speed of 72 inches asecond, past operating means such as a magnetic transducer head. Oneproblem is to efiect the tape feed positively at veryhigh speed withoutslippage of the tape and without injury to the tape surface. Anotherproblem is to initiate tape feed smoothly, to bring the tape up to speedrapidly and without tearing or snapping the tape. Still another problemis to interrupt tape feed within a reliably constant, extremely brieftime interval in order that a, desired particular section of the tape bestopped at the operating station. Thus, it may be necessary to stop thetape with an inter-block space at the operating station. The tape,moving at great speed, must therefore be brought to a halt in aninterval so short that a particularly required tape section of a verysmall fraction of an inch will be stopped at the operating station.

apparatus.

The present invention has as its general object the pro-.

vision of novel tape handling apparatus for solving the above problems.

More specifically, an object of the invention is to provide novel meansfor efiecting pneumatic clutching of the tape to or declutching fromfeed means, such as a continuously rotating capstan.

Another object of the invention is to provide a novel arrangement ofpneumatic means for stopping the tape movement substantiallyinstantaneously upon release of the tape from the grip of its feedmeans.

Another object of the invention is to provide novel magnetic means forrapidly operating a valve action to admit tape-clutching suction to orto remove such suction from tape feeding means. More specifically, it isintended to provided valve actuating means in the form of a magneticdevice involving a movable coil which, upon energization, will reactwith a fixed magnetic field to develop selfimpelling force which it willimpart to the valve action. Such magnetic device, in a very shortstroke, is capable of rapidly developing large accelerating force toeffect extremely fast and positive operation of the actuated valvestructure. The resulting time interval of operation is of exceedinglybrief duration, which can be in the order of a fraction of amillisecond.

It is also an object of the invention to provide a novel circuit for themovable coil actuator.

The tape is to be fed between reels, one at each side of the operatingmeans. To prevent excessive tension on the tape, it is formed into aloop below each reel. An

apparatus for feeding the tape selectively in either of op-- positedirections.

Other objects of the invention will become clear from the followingdescription and claims and from the accorn- V panying drawings, whichdisclose, by way of example, the.

principle of the invention and the best mode, which has beencontemplated, of applying that principle. 7 In the drawings:

. Fig. 1' is a front elevation Fig. 2 is a section through onetensioning elements.

Fig. 3 is a face view of a fragment of the magnetic record tape passingthrough the guide channel formed in the tensioning element shown in Fig.2.

Fig. 4 is a front view of one of two feeding assemblies provided in themachine and is drawn on a larger scale- Fig. 7 illustrates the circuitryof the tape feed control means.

Fig. 8 is a graph of the relations between the tape loop levels and thecontrol voltages for the reel speeds.

Fig. 9 shows the circuitry of the reel driving means.

Referring to Fig. l, the tape handling apparatus is mounted on aframework 10. Journaled on the framework are left and right tape reels11R and 11L driven by motors MR and ML, respectively. The magnetic tapeT may be fed in either direction, from the left reel .to the right orvice versa, across a centrally positioned magnetic transducer head 12.The tape is guided from one reel, say the left reel 11L, through thechanneled tracking element 13L, into a well 14L where it is formed intoa loop. From well 14L, the tape is led over a capstan15L, then throughthe channeled tape tensioning element 16L and past the transducer head12. After passing the head 12, the tape is guided through the channeledtape tensioning element 16R, over a capstan 15R and into a well 14R.-

' The tape is looped into the well and brought up, through the channeledelement 13R, onto the reel 11R.

The channeled elements 13L and R and 16L and R are similarly constructedtape guiding and tensioning devices; Each of these elements, as shownfor 16L in Fig. 2, comprises a block formed with a port 18 which opensinto a space behind a face plate 19 provided with a plurality ofapertures 1911. Port 18 is in communication with a vacuumpump 20 (seeFig. l) by means of which suction may be produced at the face plate 19to cause the tape T to be pressed to the plate. The tensioning elements16L and R are in constant communication with the pump through ducts 21and 22. On the other hand, the tensioning elements 13L and R arealternatively in communication with the pump, depending on the feeddirection. The element 13L is connected to a pipe 23L and the element13R to a pipe 2311. A solenoid-operated valve 24 is interposed betweenthe pipes 23L and R and an elbow connection to the duct 22. When thetape is feeding to the right, the valve 24 will be in such position asto admit suction only to the element 13R. During reverse feed of thetape, the valve will admit suction only to the element 13L. Thus theproper one of the elements 13L and R will be effective to produce dragonthe tape being taken up by a reel, so as to maintain the tape taut.

of the novel tape-feeding of the pneumatic, tape assume v n-aled -in afixedbracket 31. The rear end of the shaft 30 is rigidly provided with apulley 32 which is belt-driven by amotor M (seeFig, 1).. The motordrives the shafts drive connections being such as to rotate the capstan15R clockwise and the capstan 15L counterclockwise.

Secured tolthebracket 31 is a tape guide and stripper 34 which partiallysurrounds the capstan: 15", so that the a tape; is guided over the strpper. to the top :ar c' of the cap- .stan and-"then down past thestripper into the adjacent well 14. The capstanlS is formed in itsperiphery with pairs .of apertures 15a. During rotation of the capstan,the pairs of apertures 1 a successively'register with a port 31a whichis formed'in bracket 31 and in communication througha passage 31]) withthe outlet port 35a of a valve.

block 35. Valve block 3 5 is fixed to bracket 31 and its intake port 35bis connected by a duct 36 to the duct 22.

"Slidably mounted inside the valve block 35 is a valve, which may bereferred to as the capstan valve, comprising the valve head 37'fixed toa'valve stem 38 on which is also fixed a closure cylinder 39. In theposition shown in Fig. 6 the valve is in open position, allowingcommunication between the inlet and outlet ports of the valve block soas to admit suction to the capstan 15. In the open position of thevalve, the back of the valve is firmly against an annular seat 40. It isto be noted that atmosphere is acting on the back area of the valve headexposed by theseat 40, that atmosphere is also acting on the outer endof the cylinder 39, and that vacuum is being applied to the face of thevalve head. In the open position of the valve, the area of the valvehead exposed to atmosphere is appreciably less than the exposed area ofthe cylinder 39 with the result that there is a greater atmosphericforce acting on the rightend of the valve than on the left end, thedifference being adequate to maintain the valve in open position. Inclosed position of the valve, it has been shifted to the rightso thatthe valve head is 49 which is secured to the shell 46. The coil assemblyis thus mounted to the permanent magnet structure for axially slidablemovement. Fastened to the hub of the spider 48b is a rod 50 which passesfreely through a hole in its cap 49. With the valve in open position(Fig. 6),

i the left end of the valve stem'33 is against the rod 50 of i left andright hand assemblies continuously, the

the coil 48 of the magnetic unit SP. Consequently, upon axialdisplacement of this coil outwardly from the permanent magnet, the rod59 of the coil forces the valve to the right into closed position. Inthe closed position 'of the valve, the right end of its valve stem isagainst the rod 50 of the coil 48 of the'unit ST. Gutw-ard axialdisplacement of the coil of unit ST will then cause its rod 50 to shiftthe valve back to open position.

It is to be noted that the permanent magnet structure 45'-46 establishesan intense radial magnetic field across the magnetic gap 47. The axis ofthe coil 43 is at right angles to the a radial magnetic field across thegap.

" Hence, upon energization of the coil, it will be threaded with'amagnetic flux interacting with the fixed magnetic field to impel thecoil in an axial direction. The direction 1 of the energizing currentthrough the coil determines against a seat 41 andis shutting ofi thepassage between head against the seat 41, it opens the port 35a toatmos-' phere, so that airmshes into the passage 31b and the port 31(Fig. 5). Thus the pressure on both sides of the tape engaged with thecapstan is equalized and the capstan no longer grips the tape. In closedposition of the valve, the entire, area of the back of the valve head isexposed to atmosphere. This area is appreciably greater than the exposedarea of the cylinder 39 so that there is a differentlal atmosphericforce acting on the valve to maintain it in closed position. Thus whenthe valve has been shifted to. either position, it is self-maintained inthe shifted position due to a differential atmospheric force acting onthe valve in the proper direction.

The valve is shiftable from one position to the other by novel magneticactuating means comprising a pair of inagnetic units ST and SP. Eachunit includes a fixed magnet and a movable coil. In the form shown, thefixed magnet is of the permanent type embodying an alnico metal core 45and an iron shell fixed to the core in a mannerto provide a narrowannular magnetic gap 47. The movable coil 48 extends into the gap 47.This coil comprises a bobbin 48a of very light material, such as.aluminum, formed with a flanged head which is fastened into a notchedspider 481;, also of aluminum.- The outer endsof the spiderare slidablyfitted into axially parallel notches formed on the inside of the ringportion of a'cap whether it will be displaced inwardly towards oroutwardly away from the fixed magnet. In the present case, current willbe in a direction to cause outward displacement of the coil. Theexpression for the force generated in the coil at the beginning ofcurrent flow is:'

where B is the flux density at the coil due to the fixed magnet, I isthe current through the coil, and Lc is the effective length of the coilwinding. The constant 10 is a conversion factor whereby the amperes areconverted to the electromagnetic unit of current, the abampere. Theconventional ampere is one-tenth ofan abampere.

As indicated by the above expression, the force developed on the coil isproportional to the product of the fixed magnet fieldintensity and thecurrent sent through the coil. Since the current threads the coil with amagnetic flux in air,which has no finite saturation limit, the forcedeveloped on the coil can be increased without limit :byproportionallyincreasing the current. In prac-. tic e, however, thecurrent and, hence the force, is limited by the amount of current whichcan be sent through the coil without overheating the coil. -Although theforce developed onthe coil can be extremely high, the coil Consequently,in a very short stroke of the coil, which,

need .be no more than about .015 inch,the movable coil can impartsufiicient force to the valve to shift its. position with extremerapidity. In practice, the. acceleration developed has been estimated toapproximate 500 gs and the valve shifting interval has been found to bein the order of a fraction of a millisecond. Thus, the movable coilactuator can produce substantially instantaneous actuation of the valveto shut off suction from the capstan 15. or admit suction to thecapstan.

To initiate tape feed to the right, the coil 48 of the magnetic unit STof the right hand feed assembly will be energized.- Energization of thecoil will impel it outwardly to shift the valve head37 of the right handfeed assembly to open position for admitting suction tothe capstan 15R.The valve head 37 of the left hand feed assembly will remain in closedposition, shutting off suction from capstan 15L. The motors ML and MRwill be rotated counterclockwise so that the left hand reel 11L willunreel the tape while, the right hand reel 11R willtake up the tape. Thesuction force of the capstan 15R against the tape will be eliective toovercome the suction force constantly being exerted on the tape by theeither captan 15L or 15R (Fig. l).

tensioning elements 16L and R so that rotation of th capstan 15R (inclockwise direction) will draw the tape from the well 14L past thecapstan 15L, the element 16L, the magnetic head 12, and the element 16Rand into the well 14R, from which the tape will be taken up by the reel11R.

To interrupt tape feed-to the right, the coil 48 of magnetic unit SP ofthe right hand feed assembly will be energized, causing the valve head37 of this assembly to shift to the right to remove the suction from thecapstan 15R and admit atmosphere thereto. With the tape thus releasedfrom clutched contact with the capstan 15R, tensioning devices 16L and Rtake immediate efiect and substantially instantaneously stop tapemovement.

When tape feed is to take place to the left, then the direction ofrotation of the reel motors ML and MR is clockwise, the valve 24 isshifted to admit suction to pipe 23L, and the coil 48 of unit ST of theleft hand feed assembly is energized to instantly shift the valve head37 of the latter assembly to open position. The tape is thereby clutchedto the capstan 15L to be fed thereby to the left. To interrupt tape feedto the left, the coil 48 of unit SP of the left hand feed assembly isenergized causing the capstan valve of this assembly to return to closedposition, whereupon the capstan 15L releases its suction grip on thetape and the tensioning devices 16L and R immediately stop tapemovement.

Fig. 7 shows the circuits for energizing the movable coils 48 to controlthe capstan valves, and the solenoid 55 to control the-valve 24 (seealso Fig. 1). For ease of identification of the coils they aredistinguished in Fig. 7 as follows: Coil 48L-ST is the movable coil ofthe magnetic unit ST of the right hand feed assembly; coil 48L-SP is thecoil of the magnetic unit SP of the right hand feed assembly; and coils48R-ST and 4-8R-SP are the coils of the units ST and SP of the left handfeed assembly.

When the tape is not feeding in either direction, the

capstan valves of both feed assemblies are in closed positions so thatthe tape is not in feeding coaction with Further, in the normalcondition of the Fig. 7 circuits, an applied start signal will result inthe coil 48L-ST being energized to cause tape feed to the rig-ht.

Assuming the circuits are in normal condition, applica- .tion of amomentary start signal to a double stability trigger circuit TR of knownconstruction, is effective to switch conduction from gaseous dischargetube A to gaseous discharge tube B. Point 60 thereupon rises inpotential while point 61 drops in potential. Upon the rise in potentialof point 60, a positive pulse is transmitted by a small capacitor 62 tothe grid of a thyratron tube 63,

causing this tube to conduct. Current now flows from the plus 309 v.line through the tube 63, the normally closed side of contact a of arelay RV, and through the coil 48L ST to a line 64, thence through alarge capacitor C1 to ground. The current flow exponentially decays asthe capacitor C1 charges up, so that a current pulse of large amplitudebut short duration is passed through the coil ISL-ST. Thyratron 63 stopsconducting when the current decays to the extinction value but capacitorC1 is now charged. The current pulse energizes coil 48L-ST, causing itto shift the right hand capstan valve to open position, whereuponcapstan 15R (Fig. 1) is effective to feed the tape, as previouslydescribed.

interrupt tape feed, a momentary stop signal is ap plied to trigger TR,shifting conduction from tube B to tube A. Point 61 rises in potentialand a pulse is transmitted by a capacitor 65 to the grid of a thyratrontube 66, overcoming its negative bias. The charged capacitor C1thereupon discharges through the tube 66 via the normally closed side ofrelay contacts RVb through the coil 48LfiSP. The capacitor discharge isin the form of an exponentially decaying current pulse which energizesthe coil 48L-SP for shifting the right hand capstan valve 6 to closedposition, thus releasing the tape from the grip of the capstan 15R (Fig.l), in the manner previously described.

To set the machine for reverse feed, a switch 68 is closed, causingenergization of relay RV. The relay contacts RVa and b thereupontransfer disconnecting coils 48L-ST and 48L-SP from the circuit andbring coils 48RST and 48R-SP into circuit. Now, upon applica tion of thestart signal, the coil 48R-ST will be energized, and upon application ofthe stop signal, the coil 48R-SP will be energized.

It is to be noted that initiation of feed in either direction uponapplication of the start signal results in charging up the capacitor C1in readiness to discharge through tube 66 upon application of the stopsignal. During the interval between the start and stop signals, it isdesirable to maintain the charge in capacitor C1 so that it may beeffective as a source of current for the stop coil 48L-SP or 4812-31,when the stop signal is applied. To maintain the charge in the capacitorC1 during the interval between the start and stop signals, meansincluding a relay CR are provided. When the start signal is applied,causing point 60 of trigger circuit TR to rise in potential, currentflows through a rectifier 70 and the relay CR to the point 61. As longas the trigger TR remains in the state in which point 69 is at highpotential and point 61 at low potential, the relay CR remains energized.With relay CR energized, relay contacts CRa are open, removing positivepotential from the grid of a vacuum triode 71. The normal negative biasof the triode takes control and cuts it off. In cut-ofi state of thetriode, its anode is at high enough potential to condition a pentode 72to conduct. The cathode of 72 connects to line 64, so that current flowthrough the pentode is effective to maintain the capacitor C1 chargedup. When the stop signal is applied to the trigger TR, point 60 drops inpotential and point 61 rises in potential, so that relay CR isdeenergized. Relay contacts CRa close and triode 71 becomes conductive,causing its anode potential to decrease sufficiently to cut off thepentode 72. Hence, there will be no circuit for replenishing the chargein capacitor C1 which is now discharging through thyratron 66', and thecurrent pulse through the stop coil 48L-SP or 48R P will not beprolonged but will be essentiallyv a true exponentially decaying pulse.

It is to be noted that a cold cathode diode 74 is provided to maintainthe cathode potential of triode 71 at a constant level, which may be'inthe order of ---75 v. As an example each movable coil 48 may have aresistance of 10 ohms. The capacitor C1 may have a value of mfds. Thyratrons 63 and 66 may be of type C31, triode 71 oftype 61 5, diode 74of type 0A3, and pentode 72 of type 6517.

When the circuits are conditioned for reverse feed, the relay RV is inenergized condition. Relay contacts RVc are thereby closed to completethe circuit of solenoid 55. The energized solenoid adjusts the valve 24to position for admitting suction to duct 23L (Fig. 1).

Fig. 9 shows the control circuits for the motors ML and MR of the reels11L and 11R (also see Fig. 1). In the normal condition of thesecircuits, they are set consistently with the demands of tape feed to theright; that is, the motors ML and MR are prepared to receive current ina direction to cause them to rotate counterclockwise. The motor speedswill be automatically regulated according to the levels of the adjacenttape loops in the wells 14L and R (also see Fig. l).

The fields F of the motors ML and MR will be supplied with constantpotential by full wave rectifiers (not shown) in the AC. powered unitsdiagrammatically indicated by blocks 80L and 80R. The motor armatures MAwill be supplied with pulses of half wave rectified voltage by circuitsincluding thyratrons 81L and 81R, the anodes of which are connected toone side of the AC. supply. Normally, the relays RVl, 2 and 3 are notenergized.

Re ay. contac sand 1 o e y RVZ are then in dit gntti completes r u gharmature MA f m r ML as follows: from one side of the A.C. line, throughthe thyratron v 81L, the normally closed sides of relays 83L .and'RVZ,thence through armature MA of motor MLri-henormal-side of contacts b ofrelay RVZ, and to ground. Thedirection of current through the. armatureis such that the motor ML will turn counterclockwise, in apeteed re t r.At -the same ti e, current will flow through armature MA of motor .MRvia thyratron 31R, the normal side of contacts a-of relay 83R, thenormal side of contacts a of relay RV3, through armature MA of relay MR,and via the normal side of contacts 51 of RV3 to ground. The directionof currentthrough the armatureMA of motor MR'is such as to cause it toturn counterclockwise, in takeupdirection.

To condi 'on the motors ML and MR for reverse feed, the switch 68'is-closed, causing energization of relays RVl, 2, and 3. With contacts aand b of relays RVZ and 3 transferred, .the directiontof'current flowthrough armatures MA is reversed, so that motors ML and MR will turnclockwise, respectively to take up and to feed tape.

The speedsof motors ML and MR vary automatically according tothe levelsof the adjacent tape loops. The

loop levelis sensed by a set of three photocells 85 in coaction with alamp 86. Light from the lamp projects through an opening in a side of awell and the light not intercepted by the loop in the well passesthrough an opening in 'theopp'osite side of the Well to the set ofphotocells. The illumination and consequent energization of thephotocells thus vary directly as the height of the loop. Energi-zationof the photocells controls the bias on atube 87, the arrangementproviding for thebias voltage to vary inversely to the amount ofenergization of the photocells. It is clear then that the potential ofthe cathode linedesignated take-up increases as the level.

of the associated tape loop falls and decreases as the level risesConnectedto the tube 87 is a phase inverting tube 88, the output linefeed of which assumes a voltage opposite that of the line.take-up. 7

With the circuits conditioned for tape feed to the right, the relay RV1is deenergized audits contacts a and b are closed while its contacts and,d are open. The left feed line is then in series with a 90 degreelagging phase Q bias circuit 90-for the thyratron 31L, while the righthand take-up line is in series with a similarly phase-shifted biascircuit for the thyratron- 81R. The voltageof the line in series withthephase shift circuit governs the firing angle of thethyratron during thepositive half of the AC. voltage wave applied to the anode of thethyratron.

' i Fig. 8 shows the relation between the loop levels and the voltageson theo'perative feed and take-up lines. When the tape is feeding to theright and the loop level in well 14R is at the bottom, the voltage onthe right hand take-up line isgreatest. Therefore, the thyratron firingangle will be large and the motor MR will speed up, causing the reel 11Rto take up the tape more rapidly. As the loop rises, the voltage on thetake-up line de creases, the thyratron firing angle diminishes, and themotor MR reduces speed. In normal operation, the voltage on the take-upline will not exceed 16.5 v. or fall below 9 v. and the motor willoperate at a speed for maintaining the loop level within a proper range.The control of the speed of the feed motor by the voltage on theline"fee d is effected similarly but it is to be noted that the voltageon this line varies directly as the height To set the circuits forfeeding of the tape to the left,

switch 68' is closed and relays RVl, 2., and 3 are energized. With RVlenergized, the relay contacts are transferred andlplace the left handtake-up line in series .withjthe. grid phasing circuit 90 of tube 61Land the tivelyhiasesthe thyratron 81L or R, as the 'case' may be; thatthe tube will not fire at all and will not supply current to the relatedmotor armature MA. If the motor were allowed to coast to a stop, thetake-up reel might snap the tape; Therefore, means are provided topositively prevent coasting of the take-up motor when feed isinterrupted. For this purpose, the take-up? line is connected to adifferential amplifier 92 and its voltage equated against a standard of9 v. When the voltage of the ftake-up line falls below 9 v., thediiferential amplifier energizes a relay 83. In the deenergized state ofthis relay, its contacts 11 establish a charging circuit for a capacitor93. Upon energization of the relay, contacts [2 transfer and thecapacitor discharges through a relay 94. The latter relay transfers itspoints aQcompleting a circuit fer sending reverse current through thearmatureof the take-up motor. For instance, with tape feed to the righttaking place, the current supplied to the armature of motor MR bythyratron 81R is in a direction to cause counterclockwise turning of themotor. When tape feed is interrupted, differential amplifier 92R causesrelay 83R tobe energized, resulting in the energization of relay 94R. 7A circuit is thereupon completed from the -24 v. line through thetransferred contacts a of 94R, the transferred points a of relay 83R,thence via contacts a of ,RV3, through MA of motor MR and via contactsI) of RV3 to ground. The polarity of the current fed by this circuit tothe motor MR isopposite that which has been fed to the motor bythyratron 81R. Accordingly, the

. motor will tend to reverse its direction from counterto-be dynamicallybraked to a stop.

What is claimed is:

l. in a tape feeding apparatus having a mernber to pair of magneticunits each provided with an operating coil, one of said magnetic unitsoperative to move said member to said drive position and the other ofsaid magnetic units operative to move said member to said stop position,pulse producing means to selectively operate be moved between a driveposition and a stoppositiom a said magnetic units, said pulseproducingmeans including a two-condition device, a capacitor, and a controlcircuit settable by said device when in a first condition to charge saidcapacitor through the operating coil of said one magnetic unit toenergize said one magneticunit to move said movable member to said driveposition and settable 'by said device when in a second condition todischarge said device is in said first condition to maintain the chargein said capacitor.

' 2. In a tape feeding apparatus having a member to be moved between adrive position and a stop position, a pair of magnetic units eachprovided with an operating co'il, one of said'magnetic units operativeto move said memher to said drive position and the other of saidmagnetic units operative to move said member to said stoppositio'n,'pulse producing means to selectively operate saidtwo-position switch, a capacitor, and a control circuit having a firstdischarge device and a second discharge device, said control circuitsettable by said switch when in a first switch position to operate saidfirst discharge device to charge said capacitor through the operatingcoil of said one magnetic unit to momentarily energize said one magneticunit to move said movable member to said drive position and said controlcircuit settable by said switch when in a second switch position tooperate said second discharge device to drain said capacitor through theoperating coil of said other magnetic unit to momentarily energize saidother magnetic unit to move said movable member to said stop position,and a retaining circuit energized by said control circuit when saidswitch is in said first switch position to maintain the charge in saidcapacitor.

3. In apparatus having a member to be moved between a drive position anda stop position, a pair of magnetic units each provided with anoperating coil, one of said magnetic units operative to move said memberto said drive position and the other of said magnetic units operative tomove said member to said sto'p position, momentary pulsing means toselectively operate said magnetic units, said pulsing means including atwo-position switch, a bi-stable unit, a capacitor, and a controlcircuit having a first discharge device and a second discharge device,

said bi-stable unit settable by said switch when in a first switchposition to pulse said first discharge device to charge said capacitorthrough the operating coil of said one magnetic unit to momentarilyenergize said one magnetic unit to move said movable member to saiddrive position and settable by said switch when in a second switchposition to pulse said second discharge device to drain said capacitorthrough the operating coil of said other magnetic unit to momentarilyenergize said other magnetic unit to move said movable member to saidstop position, and a retaining circuit including a relay and a thirddischarge device connected to said capacitor, said relay being activatedby said bi-stable unit when said switch is in said first switch positionto render said third discharge device conductive for maintaining saidcharge on said capacitor.

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